Probing Question: How fast are the polar ice sheets melting?

April 1, 2010
By DeLene Beeland

The massive ice sheets that blanket Greenland and Antarctica are shrinking. According to the National Snow and Ice Data Center, summer melt on the Greenland ice increased by 30 percent from 1979 to 2006. Though the situation in Antarctica is less clear, scientists are also seeing loss of mass there, particularly in the fragile West Antarctic Ice Sheet.

Part of the reason, said Sridhar Anandakrishnan, a geophysicist in Penn State’s College of Earth and Mineral Sciences, is rising ocean temperatures attributable to global warming. The melting ice, in turn, raises the specter of rising sea levels. While the current rate of rise is calculated at only about an inch per decade, Anandakrishnan said, the big question is how this rate may increase over the next 50 years with continued warming.

"To predict how glaciers will respond, we need to know more about their dynamics, he said.

Anandakrishnan has traveled to Antarctica 17 times in the past 25 years to study glacial ice streams, frozen rivers of ice that flow from the center of an ice sheet and out to sea. These streams can be up to 100 miles in length, a mile deep and 50 miles wide, and most of the melting ice flows through them.

An ongoing puzzle has been the varying speed of the streams: what makes them flow faster sometimes and at other times slow down. In 2003, using seismographic instruments they designed and deployed, Anandakrishnan and his colleagues found one important clue. Their measurements showed that streams in the West Antarctic Ice Sheet flow faster in response to the fluctuations of the tides. "It was not a result we expected," he said.

In 2008, the same team showed that these tidal responses trigger slow motion "earthquakes," as the stick-slip rhythm of the moving ice sends seismic signals the equivalent of 7.0 on the Richter scale.

"The data look a lot like an earthquake," said Anandakrishnan’s co-author Douglas Wiens, a seismologist at Washington University in Saint Louis, "but the slip lasts for 10 minutes, while an earthquake of this size would last for just 10 seconds."

Other research points to further complicating factors. Anandakrishnan cites a study just published by scientists at the Scripps Oceanographic Institute which posits that wave energy originating from storms in the North Pacific Ocean is being transferred thousands of miles and destabilizing ice shelves in Antarctica. The study’s authors suggest this as an important mechanism spurring the creation or widening of crevasses on Antarctica’s ice shelves. Crevasses, Anandakrishnan explains, are deep fissures that can speed melting by shuttling melt-water to the glacier’s base, lubricating an ice stream’s movement.

"The take-away message from all this," he said, "is that the oceans and the glaciers speak to each other, if you will, more often and more strongly than we’d expect. They are not separate systems. If we’re going to understand melting and predict sea-level rise, we’ll need to understand the rhythms of their complex dance."

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10 comments

This is an interesting study. I look forward to seeing more work done in this area as it seems that there is yet one more piece of the puzzle for which we must account. Indeed, if the data holds up it will go toward explaining a few things.

It will explain why Greenland is much colder today than when the vikings were there and grew pineapples and cocoa. I have the arkeolojikal evidence here, will present it when I have time :)

The JayK sockpuppet's blathering notwithstanding, this study does not address Greenland warming and will not explain archaeological records as well as written anecdotal records of a warmer Greenland in the past than today as the study addresses Antarctica and the phenomena there.

..however I also that I have evidence the Vikings grew pineapples as written by Olaf the Great...."and the green land before me yielded abundances of Pineapples and Yam and we ceased our struggles against the Celts under yon shade of Coconuts.." This was actually found written on a stone that has only just been uncovered by a retreating glacier. I have the source somewhere...but, as usual I seem to have mislaid it..but I haven't made it up asa I did admit I had under my old name Dachpyarsewipe...honest...:)

..however I also that I have evidence the Vikings grew pineapples as written by Olaf the Great...."and the green land before me yielded abundances of Pineapples and Yam and we ceased our struggles against the Celts under yon shade of Coconuts.." This was actually found written on a stone that has only just been uncovered by a retreating glacier. I have the source somewhere...but, as usual I seem to have mislaid it..but I haven't made it up asa I did admit I had under my old name Dachpyarsewipe...honest...:)

Don't forget that even the science states that even recent Greenland warming is not unprecedented and that it warmed more quickly between 1920 and 1930 than 1995-2005.

Even AGW believing climate scientists have gone on record that there was no significant contribution of warming due to man's CO2 before 1950, so the above sockpuppet using an underscore character to misuse my username is clueless.

Here is an interesting extract taken from the above article to which I linked:

"An important question is to what extent can the current (1995-2005) temperature increase in Greenland coastal regions be interpreted as evidence of man-induced global warming? Although there has been a considerable temperature increase during the last decade (1995 to 2005) a similar increase and at a faster rate occurred during the early part of the 20th century (1920 to 1930) when carbon dioxide or other greenhouse gases could not be a cause. The Greenland warming of 1920 to 1930 demonstrates that a high concentration of carbon dioxide and other greenhouse gases is not a necessary condition for period of warming to arise. The observed 1995-2005 temperature increase seems to be within a natural variability of Greenland climate."

It is articles like the above and the one I linked which give me room for doubt on AGW. We still have much to learn before we fully understand climate change and its causes.

"To summarize, we find no direct evidence to support the claims that the Greenland ice sheet is melting due to increased temperature caused by increased atmospheric concentration of carbon dioxide. The rate of warming from 1995 to 2005 was in fact lower than the warming that occurred from 1920 to 1930. The temperature trend during the next ten years may be a decisive factor in a possible detection of an anthropogenic part of climate signal over area of the Greenland ice sheet."

Of course I know that Greenland is only a tiny piece of the earths surface, and under my other name of Dachpyisvile claimed that the '30's were the warmest globally, not just in the US...though I never could substantiate that claim :)At least I can claim that astrology is to blame for global warming...now I have admitted that the globe is indeed warming..http://legis.stat...009P.htm

Nice to know that the JayK sockpuppets just keep multiplying. Who is the troll? It is JayK and his underscore sockpuppets. Since I do not subscribe to astrological nonsense your idiocy is apparent in ways that make clear your inanity to all. Thanks for doing that to yourself.

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